Long-term evolution (LTE) system, which offers high peak data rates, low latency and improved system capacity, is adopted by many operators. In the LTE system, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNodeBs) communicating with a plurality of mobile stations, referred as user equipment (UE), via LTE-Uu interface. The radio access network further connects with a core network (CN), which includes Mobility Management Entity (MME), Serving Gateway (S-GW), and Packet data Network Gateway (P-GW), to provide end-to-end services. While LTE network increases system capacity, it is projected that LTE network may soon face capacity problems. The exponential growth of mobile subscribers requires substantial increase of network capacity. Concurrent with this problem of rapid growth of number of users, there has been a rapid uptake of Smartphone subscribers, such as iPhone, Android phone and Blackberry phone users.
Many Smartphone applications such as news, weather, and social networking, periodically connect and disconnect to/from the network for updates. These applications contain small amount of user data while still require a large amount of signaling traffic to establish and tear down the session. Consequently, the core network tends to keep UEs connected under Smartphone applications. Under diverse data application (DDA) (background/IM) environment, it is very likely to keep a UE in RRC connected mode to prevent RRC transition. Less RRC transition could have similar power saving performance if discontinuous reception (DRX) is properly configured.
However, the radio resource utilization for physical uplink control channel (PUCCH) will be a problem when the number of connected UEs increases, especially on scheduling request (SR) resources allocated in PUCCH. This is because the SR resources are dedicate and periodic, hence SR resource wastage would increase linearly as the number of connected UEs increases. For example, with a bandwidth of 10 MHz (50 physical resource blocks (PRBs)), if 300 UEs are all kept connected, then the PUCCH allocation needs 8 PRBs when SR period is 5 ms. Among the 8 PRBs, the utilization (being used resources) of SR is only 0.04% under background traffic. Even when SR period is extended from 5 ms to 80 ms, the SR resource utilization is 0.67% only. In addition, while it is straightforward to use a longer SR period to increase utilization, such allocation will increase access delay extremely. If more resources are reserved for SR, then less resources would be available for uplink data transmission via physical uplink shared channel (PUSCH) and decrease uplink capacity. Therefore, when traffic becomes more diverse, traditional unified SR resource allocation scheme may not be enough or may not be efficient to satisfy network and UE requirement.
It is an objective of the current invention to increase the SR resource utilization and to maintain QoS as well. A solution is sought.